Once a borehole has been drilled to the desired depth in an earth formation, it is necessary to lower anchors, tubing or other drill tools to the bottom of the borehole. Such devices frequently cannot pass through the drill bit and, heretofore, it has been necessary to extract the entire drill string in order to remove the drill bit. This is a time consuming and expensive process. This is particularly problematic if the earth formation is loose or unconsolidated because the borehole may cave in if the drill string is removed. To avoid this, means must provided to reinforce the borehole. This is also time consuming and expensive.
Canadian Patent No. 435,307, issued to C. Kaezor on June 18, 1946, discloses a rock drill bit having a spring wire device which facilitates assembly and disassembly of the bit in a shank or holder. This device cannot be released from a remote location, i.e. while the drill string bit is in a borehole. The drill string must be removed from the hole to release the bit.
Thus, there is a need for a drill bit latching arrangement which will allow a drill bit to be disengaged from the surface while the drill string is in situ to allow other tools and/or devices to be lowered to the bottom of the borehole.